1. Field of the Invention
This invention generally relates to a bicycle rim. More specifically, the present invention relates to a bicycle rim that is configured to reduce aerodynamic drag as the bicycle rim rotates about a center rotational axis and moves forward.
2. Background Information
There are many different types of bicycle wheels, which are currently available on the market. Most bicycle wheels have a hub portion, a plurality of spokes and an annular rim. The hub portion is attached to a part of the frame of the bicycle for relative rotation. The inner ends of the spokes are coupled to the hub and extend outwardly from the hub. The annular rim is coupled to the outer ends of the spokes and has an outer portion for supporting a pneumatic tire thereon. Typically, the spokes of the bicycle wheel are thin metal wire spokes. The ends of the hub are usually provided with flanges that are used to couple the spokes to the hub. In particular, holes are provided in the hub flanges. The wire spokes are usually bent on their inner end and provided with a flange that is formed in the shape of a nail head. The inner end is supported in one of the holes in one of the hub flanges. The outer ends of the spokes typically are provided with threads for engaging spoke nipples, which secure the outer ends of the wire spokes to holes in the rim.
Generally speaking, there are two main types of bicycle rims. The first main type of a bicycle rim is called a clincher type rim in that the rim has flanges that define annular grooves such that a wire or aramid (Kevlar) fiber bead of a tire interlocks with flanges in the rim. The above types of wheels have been, designed for use with tube tires or tubeless tires. Typically, tubeless tire wheels have an annular seal arranged to seal the spoke attachment openings of the rim. The second main type of a bicycle rim is called a tubular or sew-up rim. In tubular or sew-up rims, a tubular tire with a torus shaped is attached to the rim with adhesive. The tire engagement area of the rim is often provided with a shallow concave cross section in which the tire lies instead of flanges on which tire beads seat.
In recent years, bicycle rims have been made to be more aerodynamic. Aerodynamic bicycle rims often have a small axial dimension and a large radial dimension with respect to the center rotational axis. One example of an aero-wheel is disclosed in U.S. Pat. No. 7,114,785. In this patent, the first and second sides of wheel have a plurality of dimples. These dimples are designed to reduce aerodynamic drag.